Why Can't I Extend a C Drive With Free Space? How to Fix It?

It's troublesome that I have enough free space on my hard drive, but I can't use them to increase the size of my C drive. I tried Disk Management, and the extend volume option is greyed out. I want to know why this is happening and How I can fix this issue.

Best Answered by

Roxanne· Answered on Aug 09, 2023

Have you ever encountered an "Extend Volume greyed out and can't extend partition" problem? In this post, I will explain why this would happen and teach you how to deal with it. Check out and learn the solution to enable the C drive extension now. Regarding the reason why you can't extend the C drive even with free space, I will discuss the following primary causes:

  • The C drive is locked by another process or application, leaving you unable to resize the system partition.
  • The unallocated or free space is not behind the C drive you intend to extend. 

Now that we know why you can't resize the C drive with free space. For the first reason, you'd better close all running programs before conducting any actions on the C drive. And for the second reason, you need to turn to a professional and free partition tool EaseUS Partition Master. It can offer two practical tools that enable you to extend the C drive without adjacent unallocated space smoothly and quickly. In addition, this software is operable even if you are a computer beginner.

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Solution 1. Allocate Space

This feature will extend your C drive by allocating space from other partitions. You can learn how to use it below:

Step 1. Right-click on the partition with enough free space and choose "Allocate Space."

Step 2. Select the C drive (System partition) and drag the partition end to allocate free space from another partition to the C drive. Then click "OK."

Step 3. Click "Execute Task" > "Apply" to start allocating.

Solution 2. Adjust with 1-Click

If your C drive is full and receives a warning message for low disk space, "Adjust with 1-Click" of EaseUS Partition Master would be your best solution. Here is the complete guide on extending the C drive with "Adjust with 1-Click":

Step 1. Launch EaseUS Partition Master, which shows a low space alert in the interface. Select "Adjust with 1-Click" and click "OK" to confirm.

(You can also adjust the space using the "Manual Adjustment" option: drag the end of the C drive rightward to add free space.)

Step 2. Select the "Execute 1 Task" option and hit "Apply" to end the extending process.

If you only have one partition(C drive) on your hard drive, you can explore the method for extending the C drive from another disk in the following article:

Related Article: How to Extend C Drive from Another Disk in Windows 10/11?

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